Selective Laser Sintering and Post Processing of Fully Ferrous Components

Commercially available steel for indirect SLS (LaserFormtm A6 tool steel) is normally post-process infiltrated with a copper-based material. While such parts have high thermal conductivity necessary for short- and medium-run injection molding dies, they are weakened by the second phase with limited high temperature stability. This paper deals with a modification to the commercial process whereby a low-melting-point cast iron is substituted for the copper alloy infiltrant. A predictive model is presented that describes the part equilibrium solid fraction at the infiltration temperature as a function of the green density and infiltration temperature. In an experimental study, green parts were fabricated using LaserFormtm A6 tool steel powder. They were then heated in vacuum to drive off the binder and infiltrated with ASTM A532 white cast iron. During infiltration, an equilibrium state is established between the solid SLS steel part and liquid cast iron associated primarily with carbon diffusion from the cast iron into the tool steel. The equilibrium state is governed by the carbon content of the steel and cast iron, the relative density of the steel part prior to infiltration and the infiltration temperature. In some cases guided by Ashby densification maps, pre-sintering of the tool steel green part was performed to increase the initial relative density of the solid metal.Mechanical Engineerin

Distortions in infrastructure development in urban transport in India: How to remedy it?

National Urban Transport Policy, the guiding document for urban transport in India, emphasis movement of people and goods and not vehicles. The paper establishes that investment on walking and cycling facilities, and surface rail projects give maximum benefit compared to high cost motorised transport and metro rail. From past studies the paper also brings out that share of cycling and walking is very high – varying between 58 and 30 % in different cities. The paper identifies that contrary to benefits accrued and usage patterns, analysis of investment - both past and future projections, shows that metro rail and road development projects are preferred crowding out the other investment. The paper also identifies the reasons for distortion by identifying various groups working in the policy and their distorted perception on urban transport development. Finally the paper recommends increased investment in non motorised facilities by retrieving road space. To facilitate investment in surface rail it is necessary that Ministry of Railways, Ministry of Urban Development and Planning Commission should jointly work out the strategies. The study also recommends recasting of academic programs in urban transport to make them multi disciplinary and policy oriented

Economic Value Added --- A General Perspective

This paper explains the concept of Economic Value Added (EVA) that is gaining popularity in India. The paper examines whether EVA is a superior performance measure both for corporate reporting and for internal governance. It relied on empirical studies in U.S.A. and other advance economies. It concluded that though EVA does not provide additional information to investors, it can be adapted as a corporate philosophy for motivating and educating employees to differentiate between value creating and value destructing activities. This would lead to direct all efforts in creating shareholder value. The paper brings to attention the dangerous trend of reporting EVA casually that might mislead investors.Economic Value Added, Corporate Performace

Scaling of Fracture Strength in Disordered Quasi-Brittle Materials

This paper presents two main results. The first result indicates that in materials with broadly distributed microscopic heterogeneities, the fracture strength distribution corresponding to the peak load of the material response does not follow the commonly used Weibull and (modified) Gumbel distributions. Instead, a {\it lognormal} distribution describes more adequately the fracture strengths corresponding to the peak load of the response. Lognormal distribution arises naturally as a consequence of multiplicative nature of large number of random distributions representing the stress scale factors necessary to break the subsequent "primary" bond (by definition, an increase in applied stress is required to break a "primary" bond) leading up to the peak load. Numerical simulations based on two-dimensional triangular and diamond lattice topologies with increasing system sizes substantiate that a {\it lognormal} distribution represents an excellent fit for the fracture strength distribution at the peak load. The second significant result of the present study is that, in materials with broadly distributed microscopic heterogeneities, the mean fracture strength of the lattice system behaves as $\mu_f = \frac{\mu_f^\star}{(Log L)^\psi} + \frac{c}{L}$, and scales as $\mu_f \approx \frac{1}{(Log L)^\psi}$ as the lattice system size, $L$, approaches infinity.Comment: 24 pages including 11 figure

A Compact 1:4 Lossless T-Junction Power Divider Using Open Complementary Split Ring Resonator

This paper presents the size miniaturized and harmonic suppressed lossless 1:4 T-junction unequal power divider using an open complementary split ring resonator (OCSRR). By embedding the OCSRR structure in the microstrip transmission line, slow wave effect is introduced and thereby size reduction is achieved. The dimensions of OCSRR are optimized to reduce the length of high impedance and low impedance quarter-wavelength transmission lines. In our design high impedance line length is reduced to 58.6%, and low impedance line length is reduced to 12% when compared to the conventional quarter wavelength lines. The proposed power divider is having small dimensions of 0.18 λg × 0.33 λg and is 51.94% smaller than the conventional unequal power divider

Urinary Peptide Levels in Patients with Chronic Renal Failure

Introduction: Peptide levels in urine are found to be decreased in renal failure. In the current study urinary peptide levels were determined in chronic renal failure (CRF) patients. Method: 86 CRF patients and 80 healthy controls were selected for the study. Urinary proteins and peptide levels were determined by spectrophotometer based Lowry and Bradford methods. Urinary creatinine levels were determined by clinical chemistry analyzer. Results: There was significant decrease in urinary peptide levels in CRF patients and Urinary % peptides were significantly decreased in CRF patients as compared to healthy controls. Urinary % peptides correlated negatively with proteinuria. Conclusion: we have found decrease in urinary peptides and % urinary peptides in CRF patients and possibly measurement of % urinary peptides may possibly serve as better indicator in early detection of impairment in renal function